Since 1994 the County of Los Angeles Department of Health Services' Acute Communicable Disease Control has collaborated with CDC through its Varicella Active Surveillance Project (VASP) in Antelope Valley, CA. We propose to continue varicella and herpes zoster (HZ) active surveillance and extend the project to the city of Santa Clarita to increase the population to over 500,000. We plan to maintain active surveillance for both varicella and HZ, standardize case verification, complete case reports, document varicella vaccine usage, and continue surveillance data evaluation. VASP has collaborated with other varicella surveillance study sites in various epidemiological projects from 1994-present. We plan to conduct two applied epidemiologic research projects. The first project will evaluate if proactive on-site school varicella vaccination of susceptible students versus the standard practiceof referring children to their medical provider once the first varicella case is confirmed will decrease number of subsequent varicella cases. The second project will analyze zoster hospitalizations from 1992-2007, utilizing ICD-9 discharge codes denoted with the first 8 hospital discharge diagnoses. We will review medical charts and analyze HZ rates for incidence trends pre- and post-widespread varicella vaccine usage. Additionally, we are applying to conduct surveillance for rotavirus infection (RVI). We will utilize the existing VASP infrastructure and develop sites for RVI active surveillance throughout AV and the city of Santa Clarita. We will establish biweekly RVI data collection at active surveillance sites and will determine the incidence of RVI in clinic, emergency room, and inpatient settings. We will evaluate our system by calculating incidence of diarrhea due to RVI in hospital and emergency room utilizing ICD-9 discharge diagnosis codes for diarrhea due to RVI. When the new RV vaccine, Rotashield, is released, we will measure vaccine usage and its impact on RVI incidence.